1. Field of the Invention
Aspects of the present invention relate to an auto ignition type autothermal reformer capable of performing reproducible ignition using a catalyst layer that performs ignition without a separate ignition unit, such as an igniter or heating wire, and a fuel cell system having the autothermal reformer.
2. Description of the Related Art
A fuel cell is an electric power generation system that directly converts chemical reaction energy between hydrogen and an oxidizer into electric energy. Here, the hydrogen may be contained in a hydrocarbon-based material, such as methanol or ethanol.
A polymer electrolyte membrane fuel cell (PEMFC) and a direct oxidation fuel cell are used as representative examples of fuel cells. When methanol is used as a fuel in the direct oxidation fuel cell, it is referred to as a direct methanol fuel cell (DMFC).
Generally, the PEMFC has a large energy density and a high output. However, subsidiary or auxiliary equipment, such as a fuel reformer, are required to produce hydrogen for a fuel gas. Here, the fuel reformer is used to reform methane or methanol, natural gas, and the like.
Fuel reformers are classified into steam reformers, partial oxidation (PDX) reformers, and autothermal reformers (ATR) according to the reforming processes used. The steam reformer has high hydrogen generation efficiency. However, heat is supplied to the steam reformer by an endothermic reaction, and the steam reformer has slow response characteristics. The PDX reformer uses an exothermic reaction, does not require heat supplied thereto, and has fast response characteristics. However, the hydrogen yield of the PDX reformer is not high. The ATR uses advantages of the aforementioned two reformers, uses less energy, and has fast response characteristics.
However, the ATR is heated at a temperature over the ignition point to perform initial starting or allows an ignition spark to be generated while controlling the ratio of fuel and oxygen. Such an ignition process requires a separate balance of plant (BOP), such as a heating wire, an igniter, or a starting control device. In the ignition process, a certain amount of power is consumed, which results in an increase of cost and degradation of fuel efficiency in view of the system. Further, the structure of a reformer is complicated, which results in decreases in productivity and durability.
If an igniter is used, the noise of the igniter may have negative effects on a system circuit. To solve such a problem, a component having high price and stability is currently used. Therefore, an igniter used in a conventional ATR increases manufacturing cost of the system. Further, the use of the igniter causes the instantaneous explosion of fuel in a reactor, which results decreases the durability of the catalyst and the reactor.
Meanwhile, in a heating process, it takes time to preheat a reformer upon initial starting, and power consumption required in preheating the reformer is large. Therefore, the capacity of a battery in a system to supply power thereto is increased. Further, a heater, such as a heating wire, is easily corroded due to over-heating, and over-heating may change the properties of the heater. Therefore, it is difficult to ensure durability of the fuel reformer.